# CVE-2026-28432: HTTP signature verification can be bypassed

> Attackers can bypass HTTP signature verification in Misskey, potentially impersonating federated entities or bypassing security checks.

- **Severity:** High 7.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 9 Mar 2026
- **Updated:** 10 Mar 2026
- **Also known as:** GHSA-grwc-c762-gcvp

## What is CVE-2026-28432?

CVE-2026-28432 is a high-severity vulnerability in misskey-dev misskey, published on 9 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Misskey is an open source, federated social media platform. All Misskey servers prior to 2026.3.1 contain a vulnerability that allows bypassing HTTP signature verification. Although this is a vulnerability related to federation, it affects all servers regardless of whether federation is enabled or disabled. This vulnerability is fixed in 2026.3.1.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature)

## Which versions are affected by CVE-2026-28432?

It affects 1 product.


Products: Misskey Misskey.

## How do I fix CVE-2026-28432?

No fix has been published for CVE-2026-28432 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-28432 being exploited?

There is no known exploitation of CVE-2026-28432 in the wild and no public exploit code.

## Other vulnerabilities in misskey-dev misskey

- [CVE-2025-25306](https://insights.sbomify.com/CVE-2025-25306/): Misskey's Incomplete Patch of CVE-2024-52591 Leads to Forgery of Federated Notes (critical 9.3)
- [CVE-2023-49079](https://insights.sbomify.com/CVE-2023-49079/): Misskey's missing signature validation allows arbitrary users to impersonate any remote user. (critical 9.3)
- [CVE-2026-28431](https://insights.sbomify.com/CVE-2026-28431/): Misskey lacks proper authorization checks and input validation (critical 9.2)
- [CVE-2023-52139](https://insights.sbomify.com/CVE-2023-52139/): Misskey vulnerable to improper authorization when accessing with third-party application (critical 9.1)
- [CVE-2024-52590](https://insights.sbomify.com/CVE-2024-52590/): Missing validation allows spoofed profiles in Misskey (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-28432 and fix it if it is affected.

What it is: CVE-2026-28432 is a high-severity vulnerability in misskey-dev misskey, published on 9 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-28432 in the wild and no public exploit code.

Affected product: misskey-dev misskey. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-28432/ (Markdown: https://insights.sbomify.com/CVE-2026-28432/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-28432
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-28432
- OSV: https://osv.dev/vulnerability/CVE-2026-28432

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-28432/
Summaries are generated and may contain mistakes; the official description above is the record.